This section introduces aspects that may help facilitate a better understanding of the invention. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is prior art or what is not prior art.
On-chip voltage regulators often require a substantial area. In the case of linear regulators with high power supply rejection requirements, this area is dominated primarily by the filter capacitor and secondarily by the capacitors used to stabilize the circuit, known as stability capacitors. If two different voltages are required, then two different voltage regulators are often used, and the filter and stability capacitors are either duplicated or switched using traditional series switches.
Duplication of the capacitors results in a doubling of the largest portions of the area associated with voltage regulators. To avoid duplication of capacitors, conventional solutions that use transistors as switches in series with the capacitors either (a) require a switch similar in size to the capacitor being switched, thus negating the area benefit of reusing the capacitor, or (b) create a zero in the transfer function of the capacitor, thereby significantly reducing its capacitance.